Reservoir for storing two fluids

ABSTRACT

1,066,719. Liquefied gas storage containers. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. Jan. 12, 1966, No. 1538/66. Heading F4P. A heat insulated liquid methane storage reservoir of vertical cylindrical form is divided by a horizontal vertically movable wall (8), Fig. 1 (not shown) into a lower space (9) to which iso-pentane is admitted and withdrawn through a duct (7) and on which the wall (8) floats and into an upper space (11) to which liquid methane is admitted and withdrawn through ducts (17 to 24) extending through the reservoir side walls (3, 4) and the dividing wall (8). The latter comprises a metal box charged with compressed nitrogen and having sealing rings (15) engaging the inner wall (3). In operation and assuming the wall (8) being adjacent the reservoir top (2) liquid methane is pumped from a tanker into space (11) and the isopentane forced from space (9) into the tanker space vacated by the liquid isothane and the cold content thereof is used to liquefy gaseous methane prior to shipment. Similarly liquid methane removed from space (11) is used to liquefy gaseous isopentane prior to it being supplied to space (9). The reservoir may be mounted on a concrete foundation (6) or it may be set in a ground excavation.

April 15, 1969 I w. FRIJLINK 3,438,215

I RESERVOIR FOR STORING TWO FLUIDS Filed Dec. 19. 1966 FIG 3 INVENTOR:

WILLEM FRIJLINK HIS ATTORNEY United States Patent 01 fice 3,438,215 RESERVOIR FOR STORING TWO FLUIDS Willem Frijlink, The Hague, Netherlands, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Dec. 19, 1966, Ser. No. 602,864 Claims priority, application Great Britain, Jan. 12, 1966, 1538/ Int. Cl. F17c 13/06 U.S. Cl. 62---45 Claims ABSTRACT OF THE DISCLOSURE A container for the transport or storage of fluids is separated by means of movable wall means into a plurality of variable volume chambers to permit the withdrawal of a fluid from one of said chambers while simultaneously therewith introducing a fluid into the other of said chambers.

The invention relates to a reservoir for storing two fluids.

Gases, for example, natural gas, methane, propane, ethane or oxygen, are sometimes transported or stored in liquefied condition and at low temperature or in the socalled dense phase, that is, at low temperature and at high pressure. Liquefaction or cooling down of gases requires large quantities of energy, so that proposals have been made for restricting the energy consumption. Since the liquefied gases are normally consumed in gaseous condition, it is necessary, after storage or transport of the liquefied gases, to convert the liquefied gases into the gaseous condition. During this conversion-process cold is liberated, or in other words heat is taken in. It has already been proposed to make use of the cold liberated (absence of heat) for liquefying a next quantity of gas, by using this cold for cooling down a liquid cold-carrier. The cold-carrier cooled down in this way is then led into a heat-insulated reservoir and is stored or transported in this reservoir.

When liquefying or cooling down a next quantity of gas, the cold, present in the cold-carrier stored or supplied in the heat-insulated reservoir, is then used for liquefying or cooling down the gas.

By means of liquid cold-carriers the quantity of energy necessary for liquefying or cooling down of gas for transporting it in liquefied condition or at low temperature can be reduced substantially.

Liquid cold-carriers can also advantageously be used in peak-shaving. If, for example, the consumption of gas is small as compared to the supply of gas, a quantity of the gas supplied can be liquefield and be stored in a heatinsulated reservoir. As soon as the consumption of gas is large as compared with the supply of gas, the gas stored in liquefied condition is converted into the gaseous condition and then consumed. In other words, a quantity of gas stored in liquefied condition serves as a buffer in order to take up the peaks in the consumption of the gas. The cold liberated during the conversion of the liquefied gas into the gaseous condition is transferred to a coldcarrier. The cold-carrier thus cooled down is then stored in a heat-insulated reservoir. As soon as more gas is supplied than is consumed, the surplus of the gas supplied is liquefied, the cold present in the cold-carrier being used for liquefying the surplus gas. The gas thus liquefied is then stored in a heat-insulated reservoir.

It is remarked that, when using a cold-carrier in the way as described above, additional cooling is necessary in order to compensate for cold losses which occur during storage or transport of the liquefied gas or of the coldcarrier in heat-insulated reservoirs.

Patented Apr. 15, 1969 Reservoirs for storage or transport of the liquefied gas or of the cold cold-carrier have to be provided with a heat-insulated layer in order to be able to resist low temperatures and temperature-changes without being damaged. Therefore, these reservoirs are relatively expensive, especially if the temperatures of the liquids which have to be stored therein are low. Liquefied methane, for example, which is stored at atmospheric pressure, has a temperature of about minus C.

It is an object of the invention to reduce as much as possible the necessary investments in heat-insulated reservoirs for storing the liquefied gas, the cold gas or the cold cold-carrier in transport of liquefied gas or cold gas or in peak-shaving. This is done by using a single heatinsulated or thermal insulated reservoir for storing both the cold cold-carrier and the liquefied gas or the cold gas. The reservoir which serves accordingly for storing two cold fluids is therefore of special construction and is, according to the invention, characterized] in that it comprises a horizontal separating wall in the reservoir which wall is vertically movable, a fluid supply and outlet opening into a first space or chamber (the lower space), located below the horizontal separating wall, and a fluid supply and outlet opening into a second space or chamber (the top space) located above the horizontal separating wall.

In a suitable embodiment of the invention the horizontal separating wall is a box-like body. This box-like body can be filled with a gas, for example, with nitrogen or with another suitable gas.

The invention will be explained further with reference to the schematic drawings, in which:

FIGURE 1 shows a vertical cross-section of a first embodiment of a reservoir according to the invention;

FIGURE 2 shows a vertical cross-section of a second embodiment of a reservoir according to the invention;

FIGURE 3 shows a vertical cross-section of a fragment of the horizontal separating wall.

The top and side walls of the reservoir 1 are indicated respectively by the numbers 2 and 3. The outer surfaces of these walls are provided with a layer of heat-insulating material 5. Instead the outer and/or inner surfaces of the walls 2 and 3 can be provided with a layer of heatinsulating material. The reservoir is provided with a foundation 6, made, for example, of concrete, wood or another suitable material, and provided with heat-insulating material and a metal lining, if necessary. In the reservoir 1 a horizontal separating wall 8, movable in a vertical direction, is present. This separating wall divides the reservoir 1 in a first space or chamber 9, which may also be called the lower space or chamber 9, located under the separating wall 8, and in a second space or chamber 11, which may also be called the top space or chamber 11, located above the separating wall 8. The horizontal separating wall 8 is of about the :same construction as a conventional floating roof. In the embodiment as shown in the drawings it consists, for example, of a boxlike body, built up of metal plates 14. In top plan view the separating wall 8 is congruent to a horizontal crosssection of the reservoir 1. At its periphery the separating wall -8 is provided with a suitable seal 15, which contacts the inner surface of the wall 3. This seal 15 is shown on an enlarged scale in FIGURE 3 and comprises rings 25 and 26 made of a flexible material, for example, made of a suitable plastic, for example, Teflon. The rings 25 and 26 are vertically spaced apart and are secured to the periphery of the wall 8. Between the rings 25 and 26 a space or annular chamber 27 is present, which may be filled with a gas under pressure, for example, with nitrogen gas. The outer surfaces of the rings 25 and 26 are in contact with the inner surface of the wall 3. Within the box-like horizontal separating wall 8, a hollow space or airtight chamber 16 is present. This space or chamber 16 can be filled with a gas at a pressure higher than atmospheric, for example, with nitrogen at a pressure, for example, 7 atmospheres. The outer surface of the heat-insulating layer can be provided with an outer shell 4, for example, made of a suitable metal. The roof of the reservoir 1 is provided with a vapor outlet 29.

The reservoir 1 as shown in FIGURE 1 is provided with a fluid supply or inlet and outlet opening or port 7, opening into the lower space or chamber 9. Furthermore, the reservoir 1 is provided with a fluid supply and outlet 10, opening into the top space 11. The fluid supply and outlet t10 can be a flexible conduit assembled of a number of relatively rigid pipes, which are interconnected by suitable joints or hinges. It comprises a pipe piece 17 led through the outer shell 4, the heat-insulating layer 5 and the Wall 3. By means of a flange it is connected to a pipe piece 18, which at its turn is connected by means of a joint or hinge 20 to a pipe piece 19. The pipe piece 19 is connected to a pipe piece 21 in such a way that it is axially movable. The pipe piece 21 is connected by a joint or hinge 22 to a pipe piece 23. The pipe piece 23 is secured by means of a flange to a pipe piece 24 that is located in the separating wall 8 in such a way that it opens into the top space 11.

The reservoir as shown in FIGURE 2 is provided with a fluid supply opening into the top space 11, a fluid outlet 31 connected to the top space 11, a fluid supply 32 opening into the lower space 9 and a fluid outlet 33 connected to the lower space 9. The fluid outlet 31 comprises a pipe piece 34 arranged in the side wall 3. By means of a flange the pipe piece 34 is conneced to a pipe piece 35, which is connected by means of a joint or hinge 36 to a rigid pipe 37. The other end of pipe 37 is connected by a hinge or joint 38 to a rigid pipe 39. Pipe 39 is connected by a hinge or joint 40 to a pipe piece 40. By a flange this pipe piece 41 is connected to a pipe piece 42 passing through the wall 8.

The operation of the device described is as follows:

Assume that the lower space 9 of the reservoir 1 is entirely filled with a cold liquid cold-carrier, such as, for example, isopentane, having a temperature of, for example, minus 130 C. The separating wall 8, which floats on the isopentane, is then located in the top part of the reservoir 1. Assume that a ship, loaded with, for example, liquefied methane or natural gas having a temperature of about minus 160 C., arrives in a port where the reservoir 1 is located. The liquefied methane or natural gas is now pumped out of the ship and is passed through fluid supply 10 or 30 to the top space 11. At the same time the cold isopentane is withdrawn from the lower space 9 through outlet 7 or 33 and is pumped into empty methane or natural gas tanks of the ship. This can be continued until substantially all the isopentane has been withdrawn from the lower space 9, so that the separating wall has reached or has about reached the bottom of the reservoir 1, and until the top space 11 has been substantially filled with liquefied methane or natural gas. The cold isopentane loaded into the ship is then transported to the location where the methane or natural gas is produced. The cold present in the cold isopentane is used in said location to liquefy for transport a new quantity of methane or natural gas.

The liquefied natural gas or methane stored in the reservoir 1 has to be converted into the gaseous condition before it is consumed. During this conversion cold is liberated, or, in other words, heat has to be supplied to the liquefied natural gas or methane. This can be done by withdrawing through outlet 10 or 31 liquefied methane or natural gas from the top space 11 and by passing the liquefied methane or natural gas in heat-exchange with isopentane of about ambient temperature. Thus the isopentane is cooled down and the methane or natural gas is gasified. The isopentane cooled down in the above way is then passed through supply 7 or 32 into the lower space 9 of the reservoir 1. As more liquefied methane or natural gas is removed from reservoir .1 to be gasified, more cold isopentane is supplied to the lower space 9. The separating wall 8 is thus causes to raise, until it reaches about the top part of the reservoir 1. Then below the separating wall 8 cold isopentane is present and the reservoir 1 is then substantially completely filled with isopentane, liquefied natural gas or methane no longer present above the sepa rating wall 8.

The reservoir 1 according to the invention can be used in substantialy the same Way in peak-shaving as mentioned above.

Although in the method of using the reservoir according to the invention as described above, only liquefied methane or natural gas and the cold carrier isopentane have been mentioned, it will be clear that the reservoir can also be used for other liquefied gases and/or cold carriers. Such other gases are, for example, butane, propane, ethylene, or oxygen. Other suitable cold-carriers are liquids which, at the temperatures of the liquified gases to be stored, do not solidify or at least remain in pumpable condition.

An important advantage of the reservoir according to the invention is this, that no separate reservoirs are necessary for storing respectively the liquefied gas and the cold cold-carrier, since a single reservoir can be used for storing both.

It is remarked that the reservoir can also be located in the ground. It can, for example, be of the type having earth walls which are in frozen condition. The Walls of the reservoir located in the ground can be lined with a suitable lining, for example, made of aluminum, stainless steel, concrete, or a suitable plastic material.

The horizontal separating wall 8 can be provided with, or be made of, a suitable heat-insulating material, for example, a foamed plastic, such as foamed polyurethane.

In the example discussed the cold-carried is present below the separating wall 8 and the liquefied natural gas is present above the separating wall. The density of the coldcarrier, which is isopentane, is 800 kg./m. and the density of the liquefied natural gas is 450 kg./m. Therefore the separating wall 8 should have an average density of approximately 625 kg./m. This can be obtained by filling the separating wall 8 with nitrogen gas to a pressure which equals the maximum possible pressure on the top of the separating wall 8, which occurs when the reservoir is completely filled with liquefied natural gas, and by arranging the walls 14 at an appropriate vertical distance relative to each other.

The nitrogen present in the wall 8 will reduce heat leak from the fluid of higher temperature to the fluid of lower temperature.

The space 27 can be connected, if desired, by way of port 43 to a flexible line 44 to the outside of said storage tank so that, if there is a tendency of leakage of liquefied natural gas into the space 27, it is possible to pump liquefied natural gas through said line into the space 27, thus reducing the pressure diflerence over the top sealing ring 25. If there is a tendency of leakage from the cold-carrier side into the space 27, cold-carrier can be pumped through said line into space 27, which reduces the pressure difference over the sealing ring 26. If both sealing rings 25 and 26 are leaking, the annular space 27 can be pressurized with nitrogen gas, which reduces the pressure difference over the seal.

Instead of a liquefied gas, for example, liquefied natural gas, it is also possible to store in the reservoir gas at low temperature and at a high pressure, so that the gas is in the so-called dense phase.

I claim as my invention:

1. A thermally insulated reservoir for storing a plurality of separate fluids comprising:

an enclosed fluid storage tank having a vertical wall member;

a substantially transverse movable separating wall member slidably engaging the inner surface of said vertical wall member in sealed relation thereto;

said transverse movable wall member dividing said tank into upper and lower variable volume chambers;

a first and a second port through the wall of said tank located at a point below the lowermost downward travel of said movable wall member;

said first port being in communication with said upper chamber below said wall member and the space outside the vessel;

a third port through said movable wall member; and

means for filling said upper chamber including flexible conduit means in communication with said second and said third ports.

2. The apparatus of claim 1 including:

heat insulation means carried by said movable wall member coextensible with the major areal portion thereof.

3. The apparatus of claim 1 wherein said movable Wall comprises a pair of spaced apart plates connected together to form an airtight chamber.

4. The apparatus of claim 1 wherein the sealing engagement of said movable wall with said vertical wall member comprises a pair of spaced apart rings secured to the periphery of said movable wall and slidably engaging said vertical wall member; said rings, said vertical walls and said movable wall forming an annular chamher.

5. The apparatus of claim 4 comprising means communicating with said annular chamber and an outside space through which a pressurized fluid may be introduced.

6. The apparatus of claim 3 wherein said airtight chamher is filled with a gas under pressure.

7. The apparatus of claim '6 in which said gas is nitro gen.

8. The apparatus of claim 5 wherein said movable wall member is a heat insulating barrier between said upper and lower chambers.

9. The apparatus of claim 8 wherein said movable wall comprises a pair of plates connected together in spaced relation to form an airtight chamber.

10. The apparatus of claim 8 including a fourth and a fifth port through the wall of said tank, said first and said fourth ports forming an inlet and an outlet for said upper chamber; said second, said third and said fifth ports forming an inlet and an outlet for said lower chamber.

References Cited UNITED STATES PATENTS 2,014,264 9/1935 Patrick 48-176 2,461,537 2/1949 Field 22026 2,478,777 8/1949 Norbom 222--249 X 2,531,897 11/1950 Ulm 220-26 ROBERT A. OLEARY, Primary Examiner.

WILLIAM E. WAYNER, Assistant Examiner.

US. Cl. X.R. 22022, 26; 141284, 388; 137-578; 48-476 

